package com.bjc.principle.singleton.type5;

/**
 * @program: DesignPattern
 * @description:
 * @author: bjc
 * @create: 2020-12-13 20:40
 */
public class SingletonTest05 {
    public static void main(String[] args) {
        Singleton instance1 = Singleton.getInstance();
        Singleton instance2 = Singleton.getInstance();
        System.out.println(instance1==instance2);
        System.out.println(instance1.hashCode());
        System.out.println(instance2.hashCode());
    }
}

//懒汉式  线程安全 双重检查锁
class Singleton{
    private static volatile Singleton instance;

    private Singleton(){}

    //提供一个静态的共有方法，加入双重检查代码，解决线程安全问题
    //即懒汉式
    public static Singleton getInstance(){
        if (instance==null){
            synchronized (Singleton.class){
                if (instance==null){
                    instance = new Singleton();
                }
            }
        }
        return instance;
    }
}
